I would take a future bet that the moment we have something that can replace flash memory we will drop it like a hot rock and then tease each other about how dumb we were to entrust real data to being stored on it.
It's not like we have a choice. We don't have any robust storage technologies for normal use, so it's flash and hard drives being unreliable versus not storing data at all. Tape is the best shot for large medium-term archives, but I bet if you baby flash with a small number of writes and cool storage temperatures it'll also last 20-30 years.
